OT: Can I get some hardware advice?

I recently upgraded to CS5 and I now want to speed up my workflow with a new computer for my photography work (my current system practically grinds to a stop if I open up more than three photos at a time). I only have a budget of $1100 and this is the hardware I was considering:

Should I consider investing more in the processor or add another 2GBx3 memory kit to take me to 12GB? Also would I be better off building a RAID0 with 2 - 1TB drives or is the speed increase not worth the potential risk of drive failure?